The product range of the applicant Lechler GmbH includes a so-called water stop valve for descaling nozzles, cf. the brochure WSV “Water Stop Valve for Scalemaster Nozzles”, Lechler GmbH, January 2007. The water stop valves or check valves depicted therein comprise a tubular valve body, in which a conical shut-off member is disposed so as to be capable of movement in the longitudinal direction of the tubular valve body. The valve body is biased toward a valve seat due to the action of a compression spring. The tubular valve body is part of a nozzle tube and the valve seat is provided on a filtering element. The filtering element then forms an extension of the tubular valve body which is in turn provided with a spray nozzle at its other end. The entire nozzle tube including the spray nozzle is then partially plugged into a feed line or a welded nipple of a spray boom such that the filtering element is disposed inside the spray boom and fluid to be sprayed can flow from the feed line into the atmosphere by way of the spray nozzle. Such known check valves and nozzle tubes are used in the process of descaling hot metal surfaces, more particularly in rolling mill trains, and are intended to prevent the discharge of significant amounts of fluid from the spray nozzle when the fluid pressure drops.
It is an object of the invention to provide an improved check valve and an improved nozzle tube.
To this end, according to the invention, a check valve for a spray nozzle is provided, in which the spray nozzle comprises a valve body, a shut-off member, and a valve seat, the shut-off member being mounted so as to be capable of movement at least in a longitudinal direction of the valve body, and the shut-off member is connected to the valve body by means of a corrugated tube disposed so as to extend in a direction parallel to the longitudinal direction, and in which the shut-off member is biased toward the valve seat due to the spring effect of the corrugated tube.
The shut-off member can be connected by means of a corrugated tube to the valve body, which is tubular in shape for example, so as to be capable of movement together with said corrugated tube in the longitudinal direction of said valve body. Thus it is possible to dispense with a separate compression spring and to simplify the check valve of the invention.
In a development of the invention, pressurized fluid to be sprayed acts upon the corrugated tube both on its radially inwardly located internal surface and on its radially outwardly located external surface at least in the open state of the check valve.
In this way, there is the assurance that, even in the case of extremely high pressures of the fluid to be sprayed amounting to several hundred bar, the corrugated tube will not be deflected laterally, which might consequently alter the biasing force applied by the corrugated tube to the shut-off member. Rather, the pressures acting on the corrugated tube radially inwardly and radially outwardly thereof cancel each other out so that the corrugated tube remains capable of free movement in and against the shut-off direction of movement. In order to achieve such application of pressure to both sides of the corrugated tube, provision may be made for a first flow channel to form between the shut-off member and an internal surface of the nozzle tube, through which flow channel pressurized fluid will act upon the radially outwardly located surface of the corrugated tube. A flow channel can form between the internal surface of the nozzle tube and a shroud tube at the downstream end of the shroud tube so that pressurized fluid can act upon the radially inwardly located surface of the corrugated tube. Alternatively, the corrugated tube forms part of the flow channel with its radially inwardly located surface.
In a development of the invention, a shroud tube is provided within the corrugated tube and forms part of a fluid channel through the check valve.
The provision of a shroud tube within the corrugated tube, with the shroud tube being advantageously plain cylindrical in shape and comprising smooth walls, can ensure that there is very little flow loss in the check valve, since the shroud tube and not the corrugated tube forms part of the flow channel so that turbulences are reduced. In spite of the provision of the shroud tube, it is possible to achieve a large cross-section of free flow of the fluid flowing through the device. Advantageously, the shroud tube has a constant diameter.
In a development of the invention, the shroud tube is connected firmly at one end thereof to the shut-off member and is mounted at its other end so as to be capable of movement in relation to the valve body.
In this way, a continuous fluid channel having smooth walls can be achieved between the movable shut-off member and the opposing movable end of the shroud tube. Depending on the wall thickness of the shroud tube, there is only one step between the movable end of the shroud tube and the nozzle tube, the radial extent of the step being equal to the wall thickness of the shroud tube. The provision of a corrugated tube in place of a helical spring offers the advantage that less space is required than when use is made of a helical spring having the same biasing force. Thus a larger cross-section of free flow can be provided inside the shroud tube and lower flow loss is achieved.
In a development of the invention, the shut-off member is disposed at an upstream end of the corrugated tube as regarded in the direction of flow.
In this way, a long flow-calming region can be provided downstream of the shut-off member, which flow-calming region assists in reducing turbulences and thus in achieving reduced resistance to flow. Even at very high fluid pressures as are used on descaling nozzles, it is possible to achieve an improved spray pattern by means of the spray nozzle disposed downstream of the shut-off member and downstream of the corrugated tube.
In a development of the invention, the shut-off member is annular in shape and the valve seat is frustoconical, at least in part, and the shut-off member rests, in a closed position, on a conical surface of the valve seat.
A good sealing effect can be achieved at a low bearing pressure by means of an annular shut-off member and a frustoconical valve seat. More particularly, it is alternatively possible to design the valve seat with a flow-optimizing configuration. The annular shut-off member can be adapted to match the inside diameter of the corrugated tube so that the cross-section of free flow is not reduced in the transition region between the annular shut-off member and the corrugated tube.
In a development of the invention, the valve seat is provided on a valve seat disk that is positioned in a fluid channel of the check valve and is provided with at least one duct.
These measures improve the ease of production of the check valve of the invention, since the valve seat disk can be readily inserted into a tubular valve body.
In a development of the invention, the at least one duct is formed by means of a through bore and/or a groove in the valve seat disk. Advantageously, the at least one duct is in the form of an arcuately shaped elongated hole in the valve seat disk.
Such arcuately shaped elongated holes can be disposed so as to surround the valve seat concentrically and offer less resistance to flow than a circular bore, since a larger cross-section of free flow can be achieved and the flow needs to be deflected less sharply.
In a development of the invention, the valve seat is part of a streamlined body.
In this way, it is possible to achieve increased reduction of the resistance to flow and also to substantially improve the spray pattern of a nozzle on which liquid guided through the check valve is caused to impinge. This is of considerable advantage, particularly in the case of high fluid pressures as are applied to descaling nozzles.
In a development of the invention, the shut-off member is annular in shape and the streamlined body extends through the shut-off member.
This measure makes it possible for the fluid to be guided through the annular shut-off member and into the shroud tube when the check valve is open. Thus the flow can be significantly calmed at the critical transition point between the shut-off member and the following streamlined body or shroud tube.
In a development of the invention, the streamlined body tapers in the region of the valve seat and increases in diameter (widens) again downstream of the valve seat, as regarded in the direction of flow.
Surprisingly, the flow in the flow channel downstream of the shut-off member or valve seat can be significantly calmed when the streamlined body widens again following its tapered portion disposed in the region of the valve seat. By means of such widening of the streamlined body following its tapered region at the valve seat, the fluid is forced against the internal wall of the flow channel or the shroud tube, as a result of which, surprisingly, there are achieved a reduction in the resistance to flow and a calming effect on the flow.
In a development of the invention, the streamlined body tapers again to form an end tip following its widened portion disposed downstream of the valve seat, as regarded in the direction of flow.
The gradual taper of the streamlined body ensures reduced resistance to flow and a calming effect on the flow. The streamlined body thus tapers in the region of the valve seat, widens again following this tapered region, and then tapers off gradually to form an end tip. Advantageously, the streamlined body comprises, upstream of the valve seat, a tip which points against the direction of flow and from which point the streamlined body can then expand conically. Advantageously, the streamlined body is connected by means of individual bridges to a housing of the check valve, and these bridges form part of a valve seat disk, for example. In the region of the valve seat disk, the streamlined body can then extend parallel to the longitudinal center axis of the check valve. On the whole, the streamlined body thus exhibits an initially conically widened shape starting from a tip, as regarded in the direction of flow. The external walls of the streamlined body then extend substantially parallel to a longitudinal center axis in the region of the valve seat disk and its ducts. Following this region extending parallel to the longitudinal center axis, the streamlined body tapers to form the valve seat in this region. The valve seat is formed by a tapered region. Following a local minimum diameter, the streamlined body widens again. Advantageously, this transition from the tapered portion to the renewed widening is curved in shape. Following its widened region, the streamlined body tapers again to form an end tip. Advantageously, this transition from the widened region to the following tapered region is also curved in shape. The final tapered region extending to the end tip can be gradual and its length is equal to approximately half the length of the entire streamlined body.
The object of the invention is also achieved by means of a nozzle tube which comprises a filter and which is intended to be plugged into a feed line and which is provided with a check valve of the invention.
In such a nozzle tube, a shroud tube can be provided within the corrugated tube and the valve seat can be part of a streamlined body, and a jet straightener is disposed downstream of the streamlined body in the shroud tube in a development of the invention.
Turbulences that may not have subsided completely can be reduced further by the provision of a jet straightener in the shroud tube and a good spray pattern that remains constant over time can be achieved by means of a spray nozzle disposed on the nozzle tube even at high fluid pressures as are used on descaling nozzles.
In a development of the invention, the jet straightener comprises a plurality of flow control surfaces that extend in the radial direction toward a longitudinal center axis of the jet straightener, and a region immediately surrounding the longitudinal center axis is free from fixtures.
A good straightening effect on the flow accompanied by low resistance to flow can be achieved by means of such a jet straightener.
In a development of the invention, there is formed a fluid channel of constant cross-section downstream of the jet straightener.
Such a fluid channel of constant cross-section downstream of the jet straightener and upstream of a spray nozzle has proved to be advantageous for achieving reduced resistance to flow and a good spray pattern.
Additional features and advantages of the invention are revealed in the claims and the following description of preferred embodiments of the invention with reference to the drawings. Individual features of the various embodiments can be combined in an arbitrary manner without going beyond the scope of the invention.